Discharge valve

ABSTRACT

An improved discharge valve comprises an upper housing, an upwardly movable main valve assembly within the housing and forming with the upper part thereof a variable volume upper chamber, a restricted passage between the upper chamber and the exterior thereof, an outlet leading down from the lower part of the housing, a seat for the main valve assembly at the entry to the outlet so that, in the lowered position of the main valve assembly, the outlet is blocked against ingress of fluid in which the device is immersed, and a pilot stem actuable remotely from the housing to put the upper chamber in free communication with the outlet. The arrangement being such that, once such free communication is established, fluid escapes the upper chamber and the change in relative pressures above and below the main valve assembly causes the latter to unseat thereby permitting flow of the immersing fluid into the outlet and its substantially complete discharge. The cessation of flow of the immersing fluid allows the main valve assembly to revert to its seated position with the pilot stem cutting off free communication, and air penetrates the upper chamber and on replenishment of immersing fluid, a net downward pressure is created on the main valve assembly to keep it seated. The pilot valve has a hollow stem communicating to atmosphere above the normal full set level of fluid in the cistern. The main valve assembly and the hollow stem define therebetween a hollow annulus.

FIELD OF THE INVENTION

This invention relates to a discharge valve and is primarily intended toprovide a light action, easily operable, fast flowing valve assembly foremptying or partly emptying cisterns and other types of liquid storagecontainers. It is particularly, although not exclusively applicable tobeing used to reduce the amount of water used for flushing domestictoilets or water closets.

BACKGROUND OF THE INVENTION

For a great many years flushing toilets, pans and bowls have been inexistence, and the water closet in one form or another, is common placein all modem homes. With the conventional low flush or close coupledtoilet cistern and pan, the means for achieving the flush consistseither of a siphon (which at present for the U. K. is still the onlyacceptable device that meets the water byelaws) or one of a number ofnon-siphon type valves used extensively on the continent and elsewherein the world.

These non-siphon on direct type valves, have a valve plate or memberwhich covers and seals the outlet to prevent water from escapingunintentionally. Both the siphon and the direct type flush valve have athreaded outlet pipe which extends downwards through the bottom of thecistern into which it is fixed by a bulkhead fitting. It is thenconnected to the toilet pan either directly or by a short length ofpipe.

With the sole means of flushing or cleaning the pan being the waterdischarge from the cistern 1 the effectiveness of the flush is mainlydependent on flow rate. Most siphons do not have a good flow rate andrequire a considerable amount of water to achieve a satisfactory flush;moreover they are sensitive to changes in water level setting and mostdo not perform satisfactorily below a medium level setting. Withsome-siphon installations, the flow rates are so low that in some casesmore than one flush-is necessary.

Non-siphon type valves generally achieve greater flow rates and with thekinetic energy of the water in the pan approximately doubling for a 50%increase in flow rate, less water is required for an effective flush. Infact the performance of most U. K. toilet pans could be considerablyimproved by replacing the siphon with a direct discharge valve. Someexisting installations in the U. K. and elsewhere would accommodate evenhigher flow rates than are generally available with existing flushvalves. For new installations, by designing the galleries and contoursof the pan and cistern in conjunction with a high performance non-siphonflush valve, the quantity of water required for effective flushing couldbe substantially reduced. For instance with a valve of the typedescribed in this specification installed in the U. K. the amount ofwater required could be reduced from 7 liters to 3.5-4.5 liters fullflush capacity for all installations since January 1993 and from 9liters to 3.5-4.5 liters for installations prior to then. Moreover whenthe valve is operated in its short flush mode only 1.5-2.0 liters arerequired.

In my patent GB-B-2274344 I have described a discharge valve of improvedperformance and the present invention aims to provide furtherimprovements in this respect.

Accordingly it is an object of the present invention to provide a fluidoutlet valve to increase and enhance the performance of water closets.

It is a further object to provide a valve that can operate a full orpartial flush, a so-called dual flush valve.

It is also an object to provide a convenient overflow means through thevalve, with the added advantage of the quantity of water required forfully or partly flushing being considerably reduced.

SUMMARY OF THE INVENTION

Accordingly the invention provides a device, for immersion in a fluid ina cistern, which comprises an upper housing, an upwardly moveable mainvalve assembly within the housing and forming with the upper partthereof a variable volume upper chamber, a pressure balance hole betweenthe upper chamber and the surrounding exterior and an outlet leadingdown from the lower part of the housing, a seat for the main valveassembly at the entry to the outlet, so that in the lowered position ofthe main valve assembly the outlet is blocked against the ingress offluid in which the device is immersed, and a pilot valve, actuableremotely from the housing to put the upper chamber in free communicationwith the outlet, the arrangement being such that on this freecommunication being established fluid is ejected from the upper chamberand the change in relative pressures above and below the main valveassembly causes the latter to unseat, thereby permitting flow of theimmersing fluid into the outlet and, on its substantially completedischarge, the cessation of flow allows the main valve assembly torevert to its seated position with the pilot valve cutting off said freecommunication and air penetrates the upper chamber and on replenishmentof immersing fluid a net downward pressure is created on the main valveassembly to keep it seated, wherein the pilot valve has a hollow stem,the stem communicating to atmosphere above the desired full level offluid in the cistern, the main valve and hollow stem definingtherebetween a hollow annulus.

Thus the main path for free communication between the upper chamber andthe outlet is via the hollow annulus between the main valve assembly(piston) and the pilot valve stem.

The hollow stem protruding above the normal full level of the fluid inthe cistern provides a convenient and efficient discharge route forfluid to the outlet, should the fluid level rise above the desirednormal full level. Thus an overflow route is conveniently providedthrough the discharge valve.

To provide a dual flush facility, in addition to the main path for freecommunication; the upper chamber may, for example, be arranged toinitially communicate with the interior of the hollow stem, the top ofwhich is open to atmosphere. This additional communication is enabled,for example, by slots in the hollow stem above the pilot seat and sealedfrom the upper chamber such that only on depression of the pilot stem iscommunication between the upper chamber and its hollow stem established.

Maintaining this additional free communication by keeping the hollowstem depressed causes downwardly acting forces provided by spring ordrag means to overcome the progressively reducing upward forces on thepiston thereby resulting in air being drawn into the upper chamberfollowed by rapid premature reseating of the main valve assembly and assuch providing the means of interrupting the discharge to provide ashort flush facility. Thus in this way, either approximately half thecontents of the cistern can be discharged by holding the pilot stem downfor a few seconds, e.g. 2 or 3 seconds, or the contents can be fullydischarged by actuating the pilot stem and releasing it straightafterwards. Where drag forces are used in the dual flush embodiment,they may be provided by suitable projections on the lower part of themain valve assembly.

On cessation of flow of the immersing fluid (with the fluid level havingfallen to a level either to an intermediate level or to a level slightlyabove the valve seat) air enters either through slots or ports in thehollow stem or via the bottom of the main valve assembly allowing it todescend and revert to its seated position with the pilot valve cuttingoff free communications. As refilling takes place, some immersing fluidpenetrates the upper chamber via the pressure balance hole to create anet downward force on the main valve assembly and thereby keeping itseated. This in some cases may also be assisted by initial compressionof a control spring pressing down on top of the piston.

The immersing fluid, particularly for discharge systems of the W. C.type will of course, be water and the invention will hereafter bedescribed with reference to water for convenience.

Alternatively this additional free communication for the short flushoperation may be achieved using an auxiliary valve offset from thehollow stem and providing a vent to the upper chamber.

With all preferred embodiments the free communication of pressure withthe valve seated and the cistern filled, is via one or more pressurebalance holes between the outside of the main valve assembly and theinside of the upper chamber. To a lesser degree additional communicationcan occur between the outside of the main valve member and bore of theupper housing, but this can be kept to an insignificant amount by acentralising piston ring fitted at the top of the main valve assembly.The pilot valve which, when seated, closes off the upper chamber fromthe lower main valve assembly, hollow stem interior and outlet,co-operates with the pressure balance hole to open or close it and allowonly a restricted flow of water into and out from the upper chamber.With the main preferred configuration of the valve, the pilot valve ismoved downwards to open said passage and the main valve assembly risesto the top of the upper chamber where it remains until either theintermediate level is reached with the pilot valve held depressed oruntil the cistern is emptied by the pilot valve being depressed andimmediately released.

The upper chamber and inside the main valve assembly contain air and asmall amount of water which enters through the pressure balance hole(s).On operation of the pilot valve, air and a very small amount of waterthat is being expelled from the upper chamber by the rapidly rising mainvalve assembly enters the annular cylindrical space within the mainvalve assembly and flows downwards outside of the hollow pilot stemextension (and also in some embodiments through slots in the stem walleither above or below the pilot valve) and then down into the outlet.

Water savings of between 60 and 80% over conventional valves may beachieved by the present invention, while providing a convenient overflowprovision through the valve.

BRIEF DESCRIPTION OF THE DRAWINGS

For better understanding of the invention, various embodiments will nowbe described by way of example only with reference to the accompanyingdrawings, wherein:

FIG. 1 shows a part sectional arrangement of a device according to afirst dual flush embodiment of the invention, the valve being in theopen position;

FIG. 2 shows a view similar to FIG. 1 of a second dual flush device ofthe invention, again the valve being in the open position;

FIG. 3 is a similar view of a third dual flush device of the inventionagain with the valve in the open position;

FIG. 4 is a similar view of a fourth dual flush device of the inventionagain in the open position;

FIG. 5 is a similar view of a fifth device of the invention, being asingle flush valve in the closed position; and

FIG. 6 is a similar view of a sixth device of the invention, being asingle flush valve in the open position.

DETAILED DESCRIPTION

Thus FIG. 1 shows a cistern dual flush valve 33 fitted at the bottom ofa cistern 1 and immersed in water to set level 23 at the instant of themain valve assembly 35 having just opened and having reached the topinside of upper housing 5.

Prior to actuation the valve 33 was of course closed, with the mainvalve assembly 35 including a piston 34 in the lower position such thatthe outlet 19, which is either directly connected to the back of the panor connected by a short length of pipe, is empty and water in thecistern prevented from escaping unintentionally by main seal ring 11sealing on main seat rim 13 and pilot seal 10 sealing against pilotvalve shoulder (seat) 18. Under these conditions, with the cistern 1filled to its set level 23 upper chamber 6 is at its maximum volume andcontains mainly air (apart from a very small amount of water) at apressure equal to the depth of water in the vicinity of pressure balancehole 9. To prevent water seeping through balance hole 9, across the topof the piston head 7, into the narrow gap between boss 36 and outside ofhollow pilot stem 2 and through vent slots 44 into the hollow pilot stemand outlet 19, a seal 45 is provided. Thus seal 45 prevents water fromleaking between the outer surface of pilot stem 2 and the inner surfaceof boss 36. A slight clearance must be present therebetween to enablemovement of the pilot stem 2 inside of the boss 36. Other leakage pathswhich would occur are prevented by the caisson type overflow sleeve 58,the top edge of which determines the overflow level, and wateroverflowing this edge then gets away via slots 89 into hollow pilot stem2. An upper stem extension piece 65 of the hollow stem 2 does not playany part in the overflow condition; it is there merely to ensure thatthe operating mechanism is kept above the maximum overflow height.

With the valve seated and the cistern filled, the piston 34 is kept inthe seated condition mainly by net downward hydrostatic forces acting onthe upper piston annular area between the pilot valve shoulder 18 andthe bore of upper housing 5, the piston head 7 being sealed in the bore31 of the upper housing by centering ring 8. Other downward forces aredue to water pressure on the main seal ring 11 over the annular areabetween the main seat rim 13 and the piston body, weight of the piston34 and possibly a small amount of initial compression from a controlspring 90. The only upward force on the piston 34 in the seatedcondition is due to the water pressure acting on the annulus underneaththe piston head 7, between the piston 34 and bore 31 of upper housing 5.The hollow pilot stem 2 does not contribute to these forces, it ismaintained in the closed position or substantially the same bycompression spring 4 acting on retaining collar 3. This is so becausethe pilot stem 2 can move independently of the main valve assembly 35.This is best illustrated in the related embodiment of FIG. 5 which showsthe piston 34 in a lowered closed position and the pilot stem insubstantially the same position as in FIG. 1.

The valve 33 is operated by imparting a downward movement onto the upperstem extension piece 65 which causes the pilot stem 2 to move down,opening the pilot seal 10 and the pilot valve shoulder 18. Thisimmediately puts the upper chamber 6 in free communication with theoutlet 19 via the inner piston annular passages 16 and 25 and for thepressure in the upper chamber 6 to almost instantly fall toapproximately atmospheric pressure. As soon as this occurs the piston 34is subjected to a net upward hydrostatic force which causes the air andsmall amount of water to be slightly compressed and rapidly ejected viathe annular passages 16, 25 as the piston 34 rises to the top of theupper housing 5. (Passages 25 are provided by longitudinally-extendingfins 24 on the outside of the lower end 26--tail piece--of the pilotstem 2.). During the rise of the piston 34, additional hydrostaticforces are imparted to the piston underside profile 20 and reactionforces due to the changing direction of flow between the contours of theprofile 20 and the profile 115 substantially increase the upward forceon the piston 34. However, also as the piston 34 rises, there is anincreasing downward force due to the control spring 90 being compressed,but its stiffness is such that once the piston 34 has lifted off themain seat rim 13, the hydrostatic upward forces are sufficient to takethe piston 34 to the fully raised position in the upper housing 5.

The pilot stem 2 is provided with one or more openings or vent slots 44above its valve shoulder 18. During the opening of the valve 33 some ofthe air from the upper chamber 6 also escapes through vent slots 44 intothe hollow pilot stem 2. With the valve 33 fully open, i.e. the piston34 at the top inside the upper housing 5, the ingress of water isrestricted to a very small amount via the pressure balance hole 9 andpossibly via irregularities between the centering ring 8 and bore 31 ofthe upper housing 5, but this in total is very small and can escape fromthe bottom of the piston 34 at a rate far in excess of that at which itcan enter.

With the valve 33 open and the pilot stem 2 released straight after thedownward movement, the pilot valve shoulder 18 seals off the end of boss36 by lightly compressing the seal 45 and thus no air can flow in or outfrom the upper chamber 6. Thus the valve 33 will fully discharge thecistern 1 down to lower level 22, at which point the surface of theoutflowing water breaks clear of the lower piston edge 27 allowing airto vent upwardly into the upper chamber 6 and for the piston 34 todescend due to its own weight and the spring force and for reseating atthe profile 115 of the main seat rim 13 to take place.

In the case of the dual flush, i.e. the short flush mode, operation ofthe valve 33 is somewhat different. This time, the upper stem extentionpiece 65 is pressed down and kept down for 2-3 seconds. Again, thedownward movement opens pilot valve seal 10 and the pilot valve shoulder18 and opens up a gap below boss 36 allowing a free communicationbetween the inner piston annular passage 16 and the hollow pilot stem 2via slots 44. With this venting between the upper chamber 6 and thehollow pilot stem 2 being maintained, the hydrostatic forces actingunderneath the piston 34 reduce in proportion to the fall in water levelso that on approaching the level 51 the weight of the piston 34 andforce of the control spring 90 are sufficient to overcome the upwardforces. As air can now be sucked freely through the vent slots 44 fromthe inside of the overflow, the piston 34 rapidly descends and reseatsthus providing a short flush and discharging only approximately half thecistern contents. At the time of early reseating (short flushing) takingplace, the outlet 19 contains water which, unlike with full flushing,has to be drained by venting air from the rim of the pan, but this onlytakes a few seconds and certainly will have taken place by the time thecistern has refilled to set level 23. (Refilling may be by conventionalmeans.).

FIG. 2 shows an arrangement functionally similar to FIG. 1, butconfigurationally different, whereby the main pilot valve 92 is integralwith the upper housing 101 and the operable part of the pilot valve 92is an off set auxiliary valve 94. With this arrangement, the upperhousing 101 contains an upper chamber cavity 93 and the pilot valve seat100 and the auxiliary valve 94 are kept seated by the upward forceexerted on rod 97, which passes through a stack tube type housing 96,and which is exerted by spring 98 via auxiliary pilot spring cap 99attached to the upper end of the rod 97. The top edge of the stack tubetype housing 96 is above the maximum overflow level of the highest upperstem extension piece 65 and forms part of the same housing 96 whichcontains the overflow top pipe 91. Moreover, with this arrangementinitial communication between the upper chamber 6 and the outlet 19 isvia the upper chamber cavity 93, the auxiliary valve 94, the gallery 95and the main pilot valve 92. Equally at this point air from the upperchamber 6 will flow out through overflow top pipe 91. The contour 102 ofthe outlet 19 is different to that of FIG. 1. It can under certainconditions give a marginal increase in flow rate. However webs 103 arerequired to prevent the piston 34 from being drawn into the outlet 19 ifinstalled in a cistern 1 with exceptionally high level of water.

As before, to obtain the full flush mode the pilot valve 92 is presseddown and immediately released. In this case, of course, it is auxiliarypilot valve spring cap 99 which is pressed down to open auxiliary pilotvalve 94 which in turn allows air to escape from the upper chamber 6. Insome cases the upper chamber 6 could contain water if the pilot valve 92has been kept open during refilling, in which case the water would bepushed into the gallery 95 and then flow through the pilot valve 92 andto outlet 19. Prior to the pilot valve 92 being actuated, the pilotvalve is maintained in the closed position by the same hydrostaticforces as with FIG. 1 and when the valve is actuated the piston 34 liftsoff the pilot valve shoulder 18 and the main seat rim 13 in the sameway. In fact, functionally from hereon the action is identical to FIG. 1and thus all identical or similar parts have the same significance asbefore.

For the short flush mode the auxiliary valve 94 is opened by pressingdown on spring cap 99 and keeping it open for 2 to 3 seconds. Thus themain pilot valve 92 is opened and the piston 34 rises to the top of theupper housing 101. When the level has fallen from the set level 23 andapproaching level 51, the compressive force on control spring 90overcomes the net upward force causing the piston 34 to descend and drawair into the upper chamber 6 from the overflow gallery 95 via auxiliaryvalve 94 and cavity 93 to enable the piston 34 to rapidly descend andreseat--thus producing a short flush. All other functional aspects arethe same as for FIG. 1.

FIG. 3 is similar in arrangement to FIGS. 1 and 2, but with the upperhousing 106, pilot stem guide 54 and air stack pipe 104 being anintegral assembly which on downward deflection causes pilot seal 10,pilot valve 18 and air vent valve 111 to open.

The valve 33 in FIG. 3 is shown in the open position with the piston 34at the top, inside of upper housing 106 and with upper housing shoulder80 abutting top housing 72 and rim 109 of air stack pipe 104 seatedagainst seal pad 107. Bracket 108 is an integral part of top housing 72;seal pad 107 is attached at the top of bracket 108.

Thus, as with FIGS. 1 and 2, FIG. 3 shows a dual flush valve 33 at thebottom of cistern 1 and immersed in water soon after the main valveassembly 35 has opened and reached the top of upper housing 106 and withair vent valve 111 closed. Prior to actuation the valve 33 would ofcourse be seated with piston 34 in the lower position and the cistern 1filled to its set level 23. With the piston 34 in the lower position,water is prevented from escaping into the outlet 19 by main seal ring 11being seated on main seat rim 13 and pilot seal 10 seated on pilot valveshoulder 18. Upper housing 106 is kept in the up position by compressionspring 4 acting on retaining collar 3 via the integral pilot stem 2 tokeep upper housing shoulder 80 abutted to the underside of top housing72. This also maintains the correct position for the pilot stem guide 54for seating the pilot seal 10 and the pilot valve shoulder 18. Airtightsealing of air vent valve 111 is also achieved by this same springaction.

With the cistern 1 filled to its set level 23, upper chamber 6 will beat its maximum volume and contain mainly air at a pressure equal to thedepth of water in the vicinity of pressure balance hole 9. Air isprevented from escaping from the upper chamber by the air vent valve 111and pilot seal 10. It will moreover be noticed that the air vent valve111 is situated higher than the upper stem extention piece 65 and thatthere are no access slots in the extention piece/pilot stem 2 wall toallow air flow from the centre of the hollow pilot stem 2 to the upperchamber 6.

With the valve 33 seated and the cistern 1 filled, the piston 34 ismaintained in the seated condition mainly by net downward hydrostaticforces acting on the upper piston annular area between the pilot valveshoulder 18 and the bore of upper housing 106--the piston head 7 beingsealed in the bore and kept concentrically disposed in the upper housing106 by centering ring 8. Other lesser downward forces are due to waterpressure on the main seal ring 11 on the annular area between the seatrim 13 and piston 34, piston weight and possibly a small initialcompression from control spring 90. In the seated condition, the onlyupward force is due to water pressure acting on the annulus underneaththe piston head 7, between the piston 34 and bore of upper housing 106.The pilot stem guide 54 does not contribute to these forces, it is partof the upper housing/integral pilot hollow stem 2 and maintained in theupper position by spring 4--as described above.

The valve 33 is operated by imparting a downward movement onto upperstem extension piece 65, which causes the integral stem 2/upper housing106/stack pipe 104/pilot stem guide 54 to move downwards--which openspilot seal 10, pilot valve shoulder 18, and air vent valve 111. Thisimmediately allows air and a small amount of water to escape into theoutlet 19, which is initially empty, via the inner piston annularpassages 16 and 25 and for air to also escape from the air valve 111. Onestablishing this communication between the upper chamber 6 and theoutlet 19, almost instantly the pressure in the upper chamber drops toaround atmospheric pressure with at the same time the piston 34 suddenlybeing subjected to a net upward hydrostatic force which causes the airand the small amount of water to be slightly compressed and rapidlyejected via the annular passages 16 and 25 and causes some air to flowthrough stack pipe 104 whilst air vent valve 111 is open and the piston34 is rising to the top inside upper housing 106.

During the main valve assembly 35 rising to the open position,additional hydrostatic forces act on the piston underside profile 20 andto a lesser extent reaction forces due to rate of change of momentum offlow on contours of profiles 20, is substantially increase the upwardforce on the piston 34. As the piston 34 rises there is also anincreasing downward force due to compression of control spring 90, butthe stiffness and any initial compression is such that once the piston34 has lifted off its seat the upward hydrostatic forces are sufficientto overcome the piston weight and spring forces and take the piston 34up to the fully raised position in the upper housing 106.

Further to the initial escape of air and a small amount of water fromthe upper chamber 6 in the manner described above and the valve assembly35 fully opened, the ingress of water into the upper chamber 6 isrestricted to a very small amount via the pressure balance hole 9 andany irregularities between the outside of centering ring 8 and the baseof the upper housing 106, but in any case water can escape from theupper chamber 6 via the open pilot valve shoulder 18 into the outlet 19at a much greater rate than it can enter via said means.

With the valve 33 open and the upper housing 106 and hollow pilot stem 2released straight after downward movement, the upper housing shoulder 80abuts top housing 72 and air vent valve 11 is closed so that no air canflow into or out from the upper chamber 6 and annular passage 16. Thewater level inside the piston 34 during operation is confined to a fewmillimetres above the lower piston edge 27 in the annular passage 25.Thus with the valve assembly 35 having been opened and the air valve 111closed, the cistern 1 will fully discharge from set level 23 down toempty level 22, at which point the surface of the outflowing waterbreaks away from the lower piston edge 27, allowing air to enter andvent upwardly via annular passages 16 and 25 to the upper chamber 6 andfor piston 34 to descend, due to its own weight and the control springforce, to the reseated position.

For achieving the short flush mode, operation is initially as for thefull flush mode whereby the valve assembly 35 is opened by downwardmovement of the extension piece 65 and upper housing 106 which openspilot seal 10 pilot valve shoulder 18, and air vent valve 111 and thesudden imbalance of hydrostatic forces cause the piston 34 to rise offits seat in the same manner as already described. However, this time theupper housing 106, pilot stem guide 54 and stack pipe 104 are keptpressed down for 2 to 3 seconds. This ensures that the upper chamber 6is vented to atmosphere via air vent valve 111, which is being heldopen, and that as the water level in the cistern 1 falls from set level23 and approaches intermediate level 51, the diminishing hydrostaticforces acting underneath the piston 34 become insufficient to supportthe weight of the piston 34 and the control spring force. Moreover, withthe air vent valve 111 open and air free to flow in and out of the upperchamber 6 via stackpipe 104 and port 110, the piston 34 rapidly descendsto the reseated position and the premature closure of the valve 33leaves water in the cistern at intermediate level 51.

Venting of the outlet 19 after a short flush or interruptable flush isachieved in the same manner as that described for FIGS. 1 and 2.

FIG. 4 shows an arrangement similar to FIG. 1 except that the means forachieving the short flush is a drag ring 112 and drag disc 113 appliedto the lower part of the piston 34 instead of the control spring 90 atthe top of the piston. Also with this arrangement it is essential thatthe contour of the outlet 19 is similar to that shown in FIG. 2. Ventslots 44, 17 in the hollow pilot stem 2 are provided above and below thepilot valve shoulder 18.

The function; hydrostatic balance and basic operation is generally thesame as that described for the embodiment shown in FIGS. 1, 2 and 3 andtherefore again to produce the full flush mode the overflow extentionpiece 65/pilot stem 2 is pressed down and immediately released. Thisaction as before drops the pressure in the upper chamber 6 toapproximately atmospheric causing the main valve assembly 35 to unseatand as the main valve assembly rises to the top inside upper housing 5,air and a small amount of water is pushed downwardly via annular passage16 and through slot hole 17 (which initially is fully uncovered with thetop edge of lower piston guide boss 36 below it) into the hollow pilotstem 2 and down into the outlet 19. Initially with the hollow pilot stem2 pressed down, air can also escape through slots 44 into the hollowpilot stem 2.

With the valve 33 open, the piston 34 at the top inside upper housing 5and the slots 44 closed off by pilot valve shoulder 18 and seal 45abutting the downwardly projecting boss of the upper housing 5, theupper chamber 6 is protected against the ingress of air from the bottomof the piston 34 via the slots 17 by a controlled amount of waterentering hole 15 and surrounding the top edge of the lower piston guideboss 36. If air were allowed to enter the upper chamber 6 during thefull flush mode premature reseating of the valve assembly 35 would occurunintentionally.

In the short flush mode as with the three previous embodiments the pilothollow pilot stem 2 is pressed down and held down for 2 to 3 seconds.Unlike the other embodiments, however, the amount of downward movementis functional in creating downward forces on the piston 34. Theunderside of the pilot valve shoulder 18 engages with the top edge ofthe lower piston boss 36 causing the piston 34 to be moved down withinthe upper housing 5. Therefore, in the short flush mode with the piston34 in the lower position 1 drag ring 112 and drag disc 113 (which in thefill flush mode do not impose any significant drag) are moved to theirrespective lower positions 112A and 113A where they set up downwardforces on the piston 34 sufficient to overcome the upward hydrostaticacting underneath the piston 34 as the water level falls from the setlevel 23 and is approaching intermediate level 51. At this point withthe vent slots 44 being open air enters the upper chamber 6 from insidethe hollow pilot stem 2 causing the piston 34 to rapidly descend andreseat.

Following this short flush, the cistern 1 will refill to the set level23 and be ready for the next full or short flush.

FIG. 5 shows a full flush valve assembly 35 fitted at the bottom of acistern 1 and immersed in water at a typical filled level 23 with themain seal ring 11 seated on main seat rim 13 sealing off the outlet andwith pilot seal 10 sealing off against pilot valve shoulder 18 closingoff upper chamber 6 from the outlet. With the valve assembly 35 seatedand immersed in water, upper chamber 6 contains almost entirely air at apressure equal to the surrounding water pressure, at the depth in thevicinity of the pressure balance hole 9. Generally due to the area ontop of the main valve assembly 35 being larger than the annular areabetween the bore of upper housing 5 and main seat rim 13, a net downwardforce maintains the valve assembly in the seated condition. Also withthe valve assembly 35 seated, the annular passage 16, hollow pilot stem(overflow) 2 and outlet 19 will be empty. The pilot stem 2 is maintainedin the closed position by compression spring 4 exerting force onretaining collar 3 which in turn holds pilot valve shoulder 18 againstthe bottom of downward projecting boss 36.

The valve assembly 35 is operated by pressing the top of the pilot stem2 which as before produces a downward movement of the pilot valveshoulder 18 away from pilot seal 10 creating a substantial opening andan immediate drop in pressure in the upper chamber 6 to approximatelyatmospheric pressure. This results in a net upward hydrostatic force andfor the main valve assembly 35 to unseat and rapidly rise up into theupper housing 5 until the piston rim 37 reaches the top of the housing.This upward movement of the main valve assembly 35 causes air in theupper chamber 6 together with a small amount of water to be pusheddownwards via the pilot seal 10 and annular space passage 16 through theslots 17 into the hollow centre of the pilot stem 2. At the same time,with the main seal ring 11 lifting from main seat rim 13 a substantialopening is provided for water to flow radially inwards via ports 12 andto be deflected downwards by the contour of the lower piston undersideprofile 20 and curved diverging contour of profile 115 of the outlet 19.The flow continues downwards via narrowing profile 38 into outlet 19 andthence into the toilet pan. Also, soon after the main valve assembly haslifted off its seat rim 13, water enters the lower piston tail into thepassage 16 via access hole 15 and forming a shallow pool of water aroundthe rim 39. At the start of the valve assembly 35 beginning to rise fromits seat rim 13, air and water flow out through the slots 17 as quicklyas they enter. As the main valve assembly 35 approaches the top of theupper chamber 6 the rim 39 overlaps the top edge of the slots 17 andwater entering the hole 15 marginally rises above the rim 39 and sealsoff the space between the bore of the lower piston edge 27 and the pilotstem 2 above the top of the slots. As already described for theembodiment shown in FIG. 4, this water seal ensures that no air canenter the upper chamber 6 from the hollow pilot stem 2 via the slots 17to cause premature reseating of the valve assembly 35 once the waterlevel in the cistern 1 has fallen below the top of the main valveassembly 35 (rim 37) in the raised position. At this point there is notsufficient pressure or force underneath the main valve assembly 35 tosustain the weight of the piston 34 and thus it is essential that thepiston remains in the raised position until the cistern 1 is empty, i.e.the water level is only slightly above the seat rim 13.

With there also being the need to ensure that neither air nor waterenter the upper chamber 6 via the piston head 7 and also to accommodatefairly wide production tolerances, centralising center ring 8 is used.Some leakage is, of course, permitted via the centralising ring 8 butthis is negligible and, of course, the pressure balance hole 9 allows asmall flow into the upper chamber 6. As the water level in the cistern 1drops down to the level of hole 15, the main valve assembly 35 begins todescend under its own weight by pulling in a small amount of water viathe hole 15. The water level then drops still further until it reachesthe point at which it is level with the bottom of the lower piston edge27. This further assists with drainage of water from around the rim 39via the hole 15 by venting air up into the passage 16 and breaking thewater seal around the rim 39. This is then followed by initial downwardmovement of the main valve assembly 35 to uncover the top edges of theslots 17 and rapid venting causing the min valve assembly 35 to quicklydescend and reseat.

With the contour of the lower piston profile 20 and the profile 115 ofthe mouth of the outlet 19 being designed to achieve high hydraulicefficiency, the venturi action at the narrowing profile 38 causes apartial vacuum and for there to be little or no water inside the hollowcentre of the pilot stem 2 and therefore any communication path ortransfer passage which would enable air to enter the upper chamber 6during discharge is prevented.

FIG. 6 shows an arrangement of the fill flush valve with integraloverflow similar to FIG. 5 but with the main valve assembly 35 raised tothe top inside the upper housing 5 i.e. the valve assembly 35 open.However, there are differences in the means by which the upper chamber 6is controlled and the main valve assembly 35 kept in the raised positionto achieve a high discharge efficiency and effective fast flowingemptying down to a level marginally above the main seat rim 13. Beforeoperation,. i.e. the main valve assembly 35 closed and seated, theassembly would again be maintained in the seated mode by identicalhydrostatic seating forces as for FIG. 5. With also. the configurationof the upper part of the main valve assembly 35, pilot stem 2, spring 4and upper and lower housing assemblies being the same as before, thefunction and condition of such features as pressure balance hole 9,upper chamber 6, inner valve space 16 will also be the same as for thevalve arrangement of FIG. 5 when seated and immersed in water.

This similarity also extends to the operation and opening of the valvewherein on pressing down the pilot stem 2, pilot seal 10 and pilot valveshoulder 18 opens allowing air initially at the same pressure as thewater in the surrounding cistern 1 to escape from the upper chamber 6into the annular passage 16 and downwards through the annular passage tothe outlet 19. As before, this action causes the main valve assembly 35to lift off seat rim 13 and rise to the fully opened position with thepiston rim 37 at the top inside of the upper housing 5 and apart from asmall quantity of water that enters the upper chamber 6 via the pressurebalance hole 9 the top of the main valve assembly 35 is closed off bythe center ring 8. Of course, up to the point where mainly air is beingdischarged into the inner annular passage 16 and downwards atapproximately atmospheric pressure, operation is identical to that ofFIG. 5.

The significant features and differences of FIG. 6 are mainly in thelower part of main valve assembly 35 and downwards extension regions ofthe pilot stem 2.

Air that is being expelled from the upper chamber 6 and flowingdownwards through the annular passage 16 is turned radially inwards andenters the space defined between guide fins 24 and stem extention 40 atthe outside of pilot stem 2. It then flows downwards through an annularpassage 25, defined by the space between and outside of extensions 40 ofpilot stem 2 and boss 41 interposed by fins 24, from the bottom of whichit emerges at the lower piston edge 27 and flows beyond into the outlet19. This flow is, of course, only present whilst the main valve assembly35 is rising from its seat to the fully open position.

In the fully opened position, the highly efficient flow through thetapering duct (defined by the curved contours forming profile 20 on mainvalve assembly 35 and profile 115 of the outlet 19) creates a venturiaction at the narrowing profile 38 which, in addition to the highdownward velocity of the water impinging on the stem extension 40between the lower piston edge 27 and stem bottom 26, sets up asubstantial pressure reduction at the bottom of the piston 34 to ensurethat apart from some water at the bottom of boss 41 and annular passage25, the annular passage 16 and upper chamber 6 are drained at a rateexceeding the ingress of water, mainly from the pressure balance hole 9.

From the point at which the valve assembly 35 was operated with acistern 1 filled to set level 23, water rapidly flows through the valveassembly 35 causing the water level to fall and for this to continueuntil the cistern 1 is empty and the water level reaches its lowestlevel as indicated 22. At this point the level of water at the centresurrounding the boss 41 dips downwards and falls below lower piston edge27 allowing air to enter passage 25 and thence to the upper chamber 6causing the main valve assembly 35 to descend rapidly and reseat. Fromhere onwards refilling takes place and the cistern 1 then replenishedwith water to set level with the valve assembly closed and thereforeready for the next operation.

A number of alternative embodiments are possible. For example boss 36 inFIG. 1 could be eliminated and the height of the slots 44 raised abovethe top to position them inside the upper housing 5. This configurationwould improve short flush performance on pans with restricted galleriesand less than average performance.

I claim:
 1. A discharge valve device for immersion in a fluid in a cistern, the device comprising an upper housing, an upwardly movable main valve assembly within the housing and forming, with the upper housing, a variable volume upper chamber, a restricted passage between the upper chamber and an exterior of the upper chamber, an outlet extending downward from a lower part of the upper housing the outlet having a seat rim for the main valve assembly so that, in a lowered position of the main valve assembly, the outlet is blocked against ingress of immersing fluid in which the device is immersed, and a pilot stem actuable remotely from the upper housing to put the upper chamber in free communication with the outlet, the arrangement being such that, when such free communication is established, fluid escapes the upper chamber and the change in relative pressures above and below the main valve assembly causes the main valve assembly to unseat thereby permitting flow of the immersing fluid into the outlet and substantially complete discharge of the immersing fluid from the cistern, the cessation of flow of the immersing fluid enables the main valve assembly to revert to a seated position with the pilot stem cutting off said free communication, and air penetrates the upper chamber and on replenishment of the immersing fluid a net downward pressure is created on the main valve assembly to keep the main valve assembly seated, and the pilot stem is hollow and communicates to atmosphere above a normal full set level of the immersing fluid in the cistern, the main valve assembly and the hollow pilot stem defining therebetween an annular passage.
 2. A device according to claim 1, which operates as a dual flush valve having a short flush mode wherein a portion of the fluid in the cistern is released and a full flush mode wherein substantially all of the fluid in the cistern is released.
 3. A device according to claim 2, wherein the discharge valve device is operable in the short flush mode by maintaining a vent to atmosphere from the upper chamber via the hollow pilot stem.
 4. A device according to claim 3, wherein the vent to atmosphere from the upper chamber includes one or more slots in the hollow pilot stem above a pilot valve shoulder of the pilot stem which is to seal with the main valve assembly when the main valve assembly is closed.
 5. A device according to claim 4, wherein the pilot stem additionally has one or more openings below the pilot valve shoulder.
 6. A device according to claim 2, wherein a drag ring and a disc are provided on the main valve assembly to increase downward pressure on the main valve assembly.
 7. A device according to claim 2, wherein the pilot stem is an integral part of the upper housing.
 8. A device according to claim 7, wherein the free communication is provided by an offset auxiliary valve.
 9. A device according to claim 2, wherein the upper housing and pilot stem are formed integrally with an air stack pipe, the air stack pipe providing the free communication when the pilot stem is forced downwards by an actuating mechanism.
 10. A device according to claim 1, wherein the pilot stem is openable against pressure of a spring which returns the pilot stem to its closed position when an actuating mechanism is released.
 11. A device according to claim 1, wherein a spring in the upper chamber is compressed between the main valve assembly and the upper housing whereby in a short flush mode, when the falling fluid level approaches the desired final short flush level the returning action of the spring and weight of the main valve assembly overcome upward forces on the main valve assembly.
 12. A device according to claim 1, wherein the pilot stem has external longitudinally extending fins adjacent its lower end, which provide venting between the annular passage and the outlet when the main valve housing is in the open position.
 13. A discharge valve device for immersion in a fluid in a cistern, the device comprising:an upper housing; a movable main valve assembly within the upper housing and forming with the upper housing a variable volume upper chamber; a control spring in the upper chamber between the upper housing and the main valve assembly, the control spring biasing the main valve assembly downwardly; a restricted passage between the upper chamber and an exterior of the upper chamber; an outlet extending downward from the upper housing and main valve assembly and having a seat rim for seating the main valve assembly at the outlet in a seated position so that, in a lowered position of the main valve assembly, the outlet is blocked against ingress of fluid in which the valve device is immersed; a pilot stem actuable remotely from the upper housing to put the upper chamber in free communication with the outlet; and a compression spring biasing the pilot stem to a closed position.
 14. The device of claim 13, the device being arranged such that, when free communication is established between the upper housing and the outlet, fluid escapes the upper chamber and the change in relative pressures above and below the main valve assembly causes the main valve assembly to unseat and move upwardly, thereby permitting flow of the immersing fluid into the outlet and substantially complete discharge of the fluid, the cessation of flow of the immersing fluid enabling the main valve assembly to revert to the seated position with the pilot stem cutting off said free communication, and on replenishment of the immersing fluid a net downward pressure on the main valve assembly keeps the main valve assembly seated.
 15. The device of claim 14, wherein the pilot stem is hollow and communicates to atmosphere above a normal full set level of the fluid, the main valve assembly and the hollow pilot stem defining therebetween an annular passage. 